1. Field of the Invention
The present invention relates to a membrane circuit board switch, and more particularly, to a membrane circuit board switch with a pressure regulating reservoir.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram of a prior art membrane circuit board switch 10 used in a keyboard 12. FIG. 2 is a schematic diagram of a switch unit 32 of the membrane circuit board switch 10 shown in FIG. 1. The membrane circuit board switch 10 is used in the keyboard 12 for generating key-pressing signals. The keyboard 12 comprises a base plate 14, and a plurality of key mechanisms 16. The membrane circuit board switch 10 is installed between the base plate 14 and the plurality of key mechanisms 16. The membrane circuit board switch 10 comprises an upper membrane circuit 18, a lower membrane circuit 22, and a plurality of switch units 32. The upper membrane circuit 18 comprises a plurality of upper contacts 20. The lower membrane circuit 22 comprises a plurality of lower contacts 24 that correspond to the upper contacts 20. Each upper contact 20 and its corresponding lower contact 24 form a switch unit 32.
As shown in FIG. 2, the key mechanism 16 is up-and-down movably installed above the switch unit 32 for pressing the upper contact 20 to contact the lower contact 24 to generate a corresponding key-pressing signal. The lower membrane circuit 22 is positioned under the upper membrane circuit 18. There is an interval material layered between the upper and lower membrane circuit layers for forming a predetermined space 28 with a predetermined distance 30 between the upper and lower contacts 20, 24. When the key mechanism 16 is depressed, the upper contact 20 is pressed down to contact the lower contact 24. When the key mechanism 16 is released, or not depressed, the upper contact 20 will revert, or maintain the predetermined distance 30 from the corresponding lower contact 24.
Please refer to FIG. 3 and FIG. 4. FIG. 3 depicts a state of the switch unit 32 shown in FIG. 1 with lower atmospheric pressure. FIG. 4 depicts a state of the switch unit 32 shown in FIG. 1 with higher atmospheric pressure. Generally, there are 2 design choices of the said predetermined space 28: interacting with the atmosphere or not. To keep unwanted particles (dust, steam etc.) out of the predetermined space 28, the latter is usually chosen. However, when atmospheric pressure changes, the hermetic design of the predetermined space 28 can lead to malfunctioning of the switch unit 32. As show in FIG. 3, when the atmospheric pressure drops (this may occur due to a change of height or temperature), the pressure inside the predetermined space 28 is higher than the atmospheric pressure. Therefore, it is not easy to make the upper contact 20 to contact the lower contact 24. Furthermore, as shown in FIG. 4, when the atmospheric pressure rises, the pressure inside the predetermined space 28 becomes lower than the atmospheric pressure. Therefore, the upper contact 20 may not maintain the predetermined distance from the lower contact 24, and thus makes unexpected contact with the lower contact 24.
It is therefore a primary objective of the present invention to provide a membrane circuit board switch with a pressure regulating reservoir to solve the mention problems.
The present invention, briefly summarized, discloses a membrane circuit board switch used in a keyboard. The keyboard comprises a base plate, and at least one key mechanism. The membrane circuit board switch is installed between the base plate and the key mechanism. The membrane circuit board switch comprises an upper membrane circuit layer, a lower membrane circuit layer, and at least one pressure regulating reservoir communicates with the membrane circuit board switch. The upper membrane circuit layer comprises at least one upper contact. The lower membrane circuit layer comprises a corresponding lower contact. A predetermined space is formed with a predetermined distance between the upper and lower contacts by an interval material. The key mechanism can press the upper contact to contact the lower contact to generate a corresponding key-pressing signal. The pressure regulating reservoir communicates with the predetermined space to adjust the pressure inside the predetermined space. When the atmospheric pressure changes, the volume of the pressure regulating reservoir will adjust the pressure inside the predetermined space to make the predetermined distance keeping substantially constant.
It is an advantage of the present invention that the membrane circuit board switch prevents particles from entering the predetermined space, and it also adjusts the pressure inside the predetermined space to adapt to the changes of atmospheric pressure.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.